Internal combustion engines may be susceptible to undesired detonation under certain conditions. Undesired detonation may cause increased pressure build-up and heating that can degrade engine components as well as decrease engine efficiency. This undesirable situation is often accompanied by a certain engine noise often referred to as a ping or a knock. The ping or knock is often within a specified frequency range. As such, most approaches for identifying and addressing detonation such as engine knock often include placing acoustic sensors designed to detect the specified frequency within the engine block, cylinder head or even the intake manifold. “Knock sensors” contain piezoelectric elements that are tuned to the engine knock frequency. Vibrations from the engine knock will vibrate the piezoelectric element, which generates a voltage that can be sent to the engine control unit (ECU). The ECU will use this voltage input to detect the knock and react accordingly.
Regardless of how the engine knock is determined or reported to the ECU, current knock control countermeasures primarily rely on ignition spark adjustment, also known as “spark retard,” to mitigate and eliminate the detonation. Unfortunately, since spark is being retarded from its optimal set-point (e.g., from its “minimum spark for best torque” (MBT) set-point), the engine's operational efficiency decreases. This decrease in efficiency will degrade the vehicle's fuel economy. Moreover, the engine's output torque will reduce, compromising the vehicle's performance and its drivability. Accordingly, there is a need and desire for a knock control technique that can optimize vehicle performance and engine efficiency without compromising engine hardware protection.